1. Technical Field
The present invention relates to a surface treatment method for forming a film on the surface of treated members formed of various materials including inorganic materials such as metal, ceramic and glass, and certain inert organic materials by using atmospheric-pressure plasma, and an apparatus for practicing the method. Further, the present invention relates to a method of manufacturing a semiconductor device utilizing such a surface treatment method or a method of manufacturing an ink jet type printing head.
2. Background Art
CVD (Chemical Vapor Deposition) methods or the like are widely known as conventional methods of forming film of a high molecular compound by polymerizing a monomer. In general, in a CVD method, thin film is formed by chemical reaction on a surface heated at a high temperature of several hundred degrees or higher. On the other hand, as a technique for forming a thin film at a comparatively low temperature, plasma CVD methods are known in which excited activated species are made by electric discharge in an organic gas atmosphere at a reduced pressure of, for example, 10 to 1000 Pa to cause polymerization reaction. A method and an apparatus for polymerization using electric discharge in such a manner are described on page 216 of xe2x80x9cKhobunshi Hyomen Gijutsu (High Molecular Surface Technique)xe2x80x9d written by Toshio Fujiyoshi (edited by Khobunshi Gakkai Khobunshi Hyomen Kenkyu-Kai) and published by Nikkan Khogyo Shinbun-Sha (1987).
A polymerization method based on this plasma CVD technique, however, requires special kinds of equipment such as a vacuum chamber and a vacuum pump and, hence, a large, complicated and high-priced apparatus because the reaction takes place under a condition of reduced pressure. Moreover, for discharge processing, it is necessary to reduce the pressure in the vacuum chamber from atmospheric pressure to a vacuum, to maintain this condition and to again change the pressure from the vacuum to atmospheric pressure after discharge processing. A long time and a large amount of labor are required for this process. Further, because of a need to dispose members to be processed in the vacuum chamber, it is difficult to arrange an in-line or field process, to use a large member to be processed and to perform processing for localized film formation.
Surface treatment methods or apparatuses for forming thin film or improving a surface quality by using excited gas plasma of an organic or inorganic compound at atmospheric pressure, provided to solve the above-described problems of the conventional art, are disclosed in Japanese Patent Laid-Open Publication Nos. 306569/1989, 15171/1990, 219082/1991, 236475/1991, 241739/1991, and 358076/1992.
Further, in Japanese Patent Laid-Open Publication Nos. 263444/1991, 136184/1992 and 145139/1992 is described a method of surface-treating a base member by an atmospheric-pressure plasma treatment to make chemical plating or to manufacture a composite member.
The inventors of the present invention have also proposed, in the specification of Japanese Patent Application No. 309440/1993, a surface treatment method and an apparatus which enable good soldering on the surface of substrates or the like formed of various materials by causing electric discharge in a gas containing at least an organic material under atmospheric pressure to form excited activated species and by pre-treating the surface of the substrate or base member with the excited activated species.
The present invention has been achieved by improving the above-described conventional art and the surface treatment methods previously proposed and an object of the present invention is to provide an atmospheric-pressure plasma surface treatment method and an apparatus for use with the method which can be arranged comparatively simply for reductions in size and cost, which enable an organic material selected according to use, operating conditions and the like to be polymerized or an inorganic material to be deposited to form a film on the surface of a treated member in a short period of time in comparison with the conventional art, and which ensure improved productivity and performance suitable for an in-line/field process.
Another object of the present invention is to provide an atmospheric-pressure plasma surface treatment method which makes it always possible to achieve good adhesion between a film formed in this manner and a treated member even if the adhesion between the film and the treated member is essentially low.
Still another object of the present invention is to
provide a method and an apparatus which make it possible to perform surface treatment by generating excited activated species of an organic material comparatively safely even if the organic material used is inflammable as in many cases.
Still a further object of the present invention is to provide a semiconductor device manufacturing method which ensures that the desired insulation between bonding wires can easily be maintained even with a reduction in size of the semiconductor device (IC) and the reduction in the pitch between bonding pads with the miniaturization and the increase in density of electronic parts, whereby an improvement in yield can be achieved, and reductions in the size and the manufacturing cost of equipment and apparatus can be also achieved with a comparatively simple arrangement, which reduces the treatment time, and which makes it possible to provide an inline process and to further improve the productivity.
Still a further object of the present invention is to provide, in the ink jet printing art of providing a multiplicity of fine jet holes in a surface facing a printing surface, and performing printing by selectively jetting ink by the operation of piezoelectric elements, a printing head manufacturing method of a high productivity which enables ink to be jetted smoothly so that there is substantially no scattering or dispersion of ink, and so that sharp, fine, high-quality printing is possible, which makes it possible to reduce the size and cost of equipment and apparatus by adopting a comparatively simple arrangement, which reduces the treatment time, and which enables an inline process.
According to the present invention, there is provided an atmospheric-pressure plasma surface treatment method characterized by causing gas discharge in a predetermined discharging gas at atmospheric pressure or a pressure close to atmospheric pressure to generate excited activated species of an organic material which is liquid at room temperature, and forming a film on a surface of a treated member by using the excited activated species. This organic material may be previously included in the discharging gas to directly cause gas discharge, or may be supplied to the surface of the treated member on which the film is to be formed or to a position in the vicinity of the same to generate its excited activated species by being exposed to excited activated species of the discharge gas generated by the gas discharge.
According to the present invention, to realize the above-described atmospheric-pressure plasma surface treatment method, there is provided an atmospheric-pressure plasma surface treatment apparatus characterized by comprising means for causing gas discharge in a predetermined discharging gas at atmospheric pressure or a pressure close to atmospheric pressure, means for supplying the discharging gas to this gas discharge generation means, and means for exposing a surface of a treated member to excited activated species of an organic material which is liquid at room temperature, the excited activated species being generated by the gas discharge.
According to the present invention, this organic material may be variously selected to polymerize an organic material on the surface of the treated member so that a film having various characteristics according to use can easily be formed, or so that the film formation speed is increased to improve the surface treatment ability and the productivity. If the organic material is silicone, a fluoric solution or a hydrocarbon, a water-repellent film is formed on the surface of the treated member. In the case of an organic material having a hydrophilic group, a film having high hydrophilic property is formed. In the case of silicone, an unsaturated compound, a cyclic compound or an organic metallic compound, the hardness of the surface of the treated member can be increased by the formed film. Further, if the organic material is an unsaturated compound, a cyclic compound or a compound having a crosslinking structure, the film forming speed of the polymerized film can be largely increased.
According to the present invention, if the discharging gas comprises a gas of nitrogen or fluorocarbons, the formation of the polymerized film of the organic material can be promoted. Conversely, if a gas of oxygen or a chemical compound containing oxygen is supplied, the polymerization of the organic material can be limited. Therefore, it is possible to partially limit the formation of the polymerized film according to a need by selectively feeding such a gas to the surface of the treated member and to a region surrounding the same separately from the discharging gas and by controlling the distribution of the gas.
According to the present invention, there is also provided an atmospheric-pressure plasma surface treatment method characterized by comprising causing gas discharge in a predetermined discharging gas at atmospheric pressure or a pressure close to atmospheric pressure to generate excited activated species of oxygen and an organic material which is liquid at room temperature and which contains inorganic element, and forming a film on a surface of a treated member by using the excited activated species. According to this method, the existence of oxygen enables the inorganic element contained in the organic material or an oxide of the organic element to be formed as a film.
According to the present invention, the film formation by gas discharge can be continued while the amount of oxygen used is being reduced. In such a case, it is possible to gradually change the film on the surface of the treated member from a film of an inorganic material to the polymerized film of the organic material. Therefore, even if the adhesion of the polymerized film of the organic material to be formed on the surface of the treated member is low, it is possible to form a polymerized film by first forming a film of an inorganic element or an oxide of the same having good adhesion and by thereafter adjusting the amount of used oxygen so that the desired polymerized film is finally completed.
According to the present invention, there is further provided an atmospheric-pressure plasma surface treatment method characterized by comprising causing gas discharge at atmospheric pressure or a pressure close to atmospheric pressure in a predetermined discharging gas of oxygen or a compound containing oxygen or nitrogen to generate excited activated species, and forming a film on a surface of a treated member by using the excited activated species. According to this method, the surface of the treated member can become hydrophilic.
According to the present invention, there is provided an atmospheric-pressure plasma surface treatment method characterized by comprising mixing an organic material which is liquid at room temperature in a discharging gas by heating the organic material at a temperature not higher than its flash point of the material so that organic material is evaporated, causing gas discharge in the discharging gas at atmospheric pressure or a pressure close to atmospheric pressure to generate excited activated species, and forming a film on a surface of a treated member by the excited activated species. This method ensures that an inflammable organic material can be safely mixed in discharging gas to cause gas discharge.
In the present invention, if two or more organic materials which are liquid at room temperature are used, each material is evaporated by being heated and the materials are mixed in discharging gas in the order of the lowest to the highest of the boiling points of the organic materials. Accordingly, with respect the temperature at which one organic material is heated, the temperature of another organic material which is to be next mixed is heated can be higher. Therefore, there is no possibility of the preceding organic material mixed in the discharging gas liquefying by being cooled by the subsequent organic material.
According to the present invention, there is further provided a method of manufacturing a package type semiconductor device by connecting an electric part and leads by wires and by sealing them in a resin, the method being characterized by comprising the steps of causing gas discharge in a predetermined discharging gas at atmospheric pressure or a pressure close to atmospheric pressure before the electronic part and the leads connected by the wires are sealed in the resin, generating, by the gas discharge, excited activated species of an organic material which is liquid at room temperature, and forming an insulating film on the surfaces of the wires by using the excited activated species.
According to the present invention, there is further provided a method of manufacturing an ink jet type printing head having an ink jet surface in which a multiplicity of fine holes for selectively jetting ink are formed by being opposed to a printing side, the method being characterized by comprising the steps of causing gas discharge in a predetermined discharging gas at atmospheric pressure or a pressure close to atmospheric pressure, generating, by the gas discharge, excited activated species of an organic material which is liquid at room temperature and which is silicone, a fluoric solution or a hydrocarbon, and forming a film on the ink jet surface by using the excited activated species.